The present invention relates to systems for transmitting electric signals, electric power, liquids, gases and other media over short distances between units movable relative to each other. Depending on the type of the movement, these are encompassed by various terms such as contact lines, slip rings or generally rotary transmission systems.
So-called contact lines are used to transmit electric signals or electric power with a preferably linear or slightly curved trajectory. In the event of rotary movements, these elements are referred to as slip rings. For non-contacting transmission between mated parts or units movable relative to each other, various systems are known, for example the system described in the European Patent Application 98 907 894.4-2206 and comprising a conductor-like structure composed of discrete dummy elements. Moreover, so-called rotary transmitters are known for liquids and gases, particularly in the event of transmission between mated parts or units rotating relative to each other. As a rule, such transmission systems are highly important for the function of the overall system. They are often even classified as critical components. If, for example, the signaling function would fail between the rotor and the stator in a computer tomograph, the emitter performance of the X-ray tube could no longer be controlled. As a consequence, the patient could be exposed to an excessive radiation dose. In the case of a crane installation movable along a linear path, the failure of the emergency stop device could lead to catastrophic consequences. It is therefore definitely necessary in all of these applications to monitor the transmission path. This is frequently achieved by monitoring the data communication between the transmitter and the receiver, with a great number of different components being often integrated into this data path in its entirety. The overall system of the transmission path is hence monitored. This known concept, however, entails the disadvantage that individual failed or faulty components cannot be located. This disadvantage is substantially more serious when the fault modes of isolated transmission components are considered. When mechanical sliding contact arrays, especially slip rings, are used for signal transmission, various fault constellations may occur. When, in the simplest case, the sliding path is soiled, for instance, this may result in sporadic failure events. Such faults can often still be absorbed by a system fault correction function. As soon as the first sporadic transmission faults occur, it is possible in such a case to clean the system again and to repair it. When the carbon or graphite brushes are worn to a maximum extent, however, massive faults occur in transmission suddenly because the brushes lift off the sliding path and can no longer establish a contact. Here, a pre-signaling period from the first failure up to total breakdown is comparatively short. The effects are substantially more serious in non-contacting transmission paths. When, for example, the transmitter output power decreases continuously, due to electronic components aging, it is possible that one day the signal amplitude will drop below the input response threshold of the receiver and that data transmission is no longer possible. This may result in an abrupt system breakdown without pre-signaling interval. In the case of liquid transmitters, the leakage of slight quantities of liquid is sufficient to result in serious damage to neighboring electronic components or other parts.
In the description below, no distinction is made between stationary and movable because such a distinction is only a question of the definition of the reference system.